Pressure responsive timing device

ABSTRACT

The present invention relates to a time-delay device or timer and more particularly to a mechanical time-delay device having a switch for opening or closing an electric circuit at a selected future time wherein an expansible member within a compressed fluid chamber actuates the switch when the pressure of the chamber decreases.

United States Patent Gerald E. Hart Washington, D.C.

Aug. 30, 1965 Oct. 19, 197 1 The United States of America as represented by the Secretary of the Navy Inventor Appl. No. Filed Patented Assignee PRESSURE RESPONSIVE TIMING DEVICE 14 Claims, 4 Drawing Figs.

U.S. Cl 200/33, l02/75,307/118 Int. Cl H01h 43/02 Field of Search 200/33, 34,

[5 6] References Cited UNITED STATES PATENTS 3,230,323 1/1966 Concannon 200/33 Primary ExaminerRodney D. Bennett, Jr Assistant Examiner-N. Moskowitz Attorneys R. S. Sciascia and R. l. Tompkins ABSTRACT: The present invention relates to a time-delay device or timer and more particularly to a mechanical timedelay device having a switch for opening or closing an electric circuit at a selected future time wherein an expansible member within a compressed fluid chamber actuates the switch when the pressure of the chamber decreases.

PATENTE'UBU 19 ml 3.614.348

SHEET 1 [1F 2 7e I 2 75 77 76 7* 56 y 59 INVENTOR GERALD E. HART ATTORNEY PRESSURE RESPONSIVE TIMING DEVICE The present invention relates to a time-delay device or timer and more particularly to a mechanical time-delay device having a switch for opening or closing an electric circuit at a selected future time wherein an expansible member within a compressed fluid chamber actuates the switch when the pressure of the chamber decreases.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

In the past, several types of timers have been used which have proven complex andunreliable. In most cases, mechanical timers have been employed which have been highly susceptible to damage by dust, temperature and humidity. Many mechanical timers employ clock mechanisms which have the disadvantage of being noisy and easily detectable because of their ticking sound. In many applications this is a serious disadvantage. In addition, highly reliable clock mechanisms are very expensive, so that high reliability is only obtained through unnecessarily high cost. Furthermore, clock-type mechanisms are susceptible to rust and corrosion in the warm and humid climates so that their operation is drastically limited.

The general purpose of this invention is to provide a timedelay device or timer which embraces all the advantages of similarly employed devices and which possesses none of the aforedescribed disadvantages. This invention is highly reliable because of the very simple construction and the avoidance of moving parts, such as shafts, gears, and bearings. This device is less expensive than a comparable timer employing a clock mechanism. It is practically foolproof and its operation and reliability are not effected by temperature, humidity, dust, or even immersion in water. To attain this, the present invention contemplates a time-delay device or timer comprising a housing or capsule defining a compressed air chamber having a switch therein which is closed at a preset time by an expansible member such as a rubber balloon which expands when the air pressure in the chamber has dropped sufficiently. The air in the chamber is allowed to discharge through a metering valve which is adjustable to control the rate of airflow out of the chamber thereby controlling the rate of expansion of the expansible member to provide a desired time-delay. The switch is electrically connected to the exterior of the chamber housing to terminals which may be utilized to electrically connect an external device or circuit to be actuated by the timedelay switch.

An object of the present invention is the provision of an inexpensive novel timer of high reliability.

Another object is to provide an accurate mechanical timer which is simple to operate and noiseless.

A further object of the invention is the provision of a mechanical timer which is highly reliable and whose operation is unaffected by temperature, humidity, dust or even immersion in water.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when consideration in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is a cross-sectional view along the longitudinal axis of an embodiment of this invention;

FIG. 2 is a cross-sectional view of another embodiment of this invention;

FIG. 3 is a cross-sectional illustration of a third embodiment of this invention;

FIG. 4 is a cross-sectional illustration of a fourth embodiment of this invention.

Referring now to the drawings there is shown FIG. 1 a fluidtight capsule or shell 11 defining a compressed air chamber 12 having internal struts 13, 14, 15 and 16 for supporting a spherical screen enclosure 17 having fixed contacts 18 and 19 about its periphery. Contacts 18 and 19 are electrically connected by wires 21 and 22 to electrical terminals 23 and 24, respectively, of shell 11. Contacts 25 and 26 are connected electrically by springs 27 and 28, respectively, to contacts 31, and 32, respectively, of screen enclosure 17. Contacts 31 and 32 are electrically interconnected by means of wire 33, so that when contacts 18 and 25 engage, and contacts 26 and 19 engage, a complete circuit is made between terminals 23 and 24. The contacts about cylindrical screen enclosure 17 must be insulated from the screen so that there is no electrical connection or short between all the contacts about the periphery of the screen. Insulation is obtained by either directly insulating the contacts from the screen enclosure 17 by use of any suitable insulating means or by providing a screen enclosure which is electrically nonconductive. Within the screen enclosure 17, and between springs 27 and 28, is a freely supported expansible container 35 such as a gas filled rubber balloon.

Shell 11 also has a first valve 36 for allowing air to enter for pressurizing the chamber. A metering'type valve 37 is also provided for allowing air under pressure within the shell to exit from the chamber. The valve is adjustable to vary the rate at which the air leaves the chamber. Metering valve 37 comprises orthogonally related orifices 38 and 39 having a set screw 41 at their junction. By means of metering valve 37 the air within the compressed air chamber 12 is allowed to exit or discharge slowly at a predetermined rate which is controlled by set screw 41. The rate of air discharge determines the rate of expansion of expansible container 35. v

In operation, as the pressure inside the chamber decreases due to the discharging air, balloon 35 expands until it forces spring contacts 25 and 26 against the fixed contacts 18 and 19, respectively, at which time the circuit between terminals 23 and 24 is completed. If desired, chamber 12 may then be recharged for repeated operations by connecting a high-pressure hose to valve 36 and again raising the pressure of the chamber to the desired level and returning expansible container 35 to its substantially unexpanded or contracted condition. Temperature compensation is provided by employing a bimetallic structure for springs 27 and 28. By means of these bimetallic springs the time-delays produced are more accurate since they are virtually independent of temperature variations.

A second embodiment of the invention is illustrated in FIG. 2, wherein the fiuidtight enclosure for the compressed air chamber is of a cylindrical configuration. In this embodiment cylindrical housing 51 encloses a compressed air chamber 52 having an internal support 53 for supporting a cylindrical screen enclosure 17 having a pair of microswitches 54 and 55 positioned at diametrically opposed points about its periphery. Microswitches 54 and 55 are electrically interconnected in series by wire 56. Microswitch 54 is serially connected with arming switch 57, battery 58, and terminal 59 which is mounted on housing 51 extending therethrough and insulated therefrom. A second terminal 61 is also mounted on and insulated from housing 51. Terminal 61 extends through the housing for electrical connection to microswitch 55 so that a complete circuit is made between terminals 59 and 61 when microswitches 54 and 55 are actuated together with arming switch 57. At that time the voltage of battery 58 appears across terminals 59 and 6!.

Attached to screen enclosure 17 of FIG.'2 are Springs 27 and 28 having contacts 25 and 26 at the ends thereof adjacent to microswitches 54 and 55, respectively. Within screen enclosure 17 is an expansible container or balloon 35 for forcing spring contacts 25 and 26 against buttons 63 and 64, respectively, of microswitches 54 and 55 when balloon 35 sufficiently expands as the air pressure within chamber 52 decreases.

Cylindrical housing 51 has a front plate 72 having a valve 73 for pressurizing chamber 52 mounted on the inner wall of plate 72. A pressuretight cap screw 74 is provided which is threadedly engaged into plate 72 in order to eliminate the possibility of a leaky valve. A valve 75 with a calibrated orifice 76 therethrough is mounted on the inner wall of plate 72 and a threaded opening is provided through plate 72 which is recessed for receiving pressure tight cap screw 77 for preventing discharge of air until the cap is removed. Arming switch 57 is also mounted on the inner wall of plate 72 aligned with an opening through plate 72 which is threaded for receiving a third pressuretight cap screw 78 for actuating arming switch 57. A battery terminal 81 is mounted on and insulated from a cylindrical housing 51 while a second battery terminal 82 is attached to terminal 59. It is to be noted that each opening in the housing is made pressure tight by means of a screw cap equipped with a gasket or O-ring" (not shown). The cap 77 to timing orifice 76 has a slot in the thread so that the exit of gas is unrestricted when the cap is unscrewed by two or three turns. Battery 58 is mounted internally for convenience only and may, of course, be connected in an external circuit.

FIG. 3 is a third embodiment of this invention. This embodiment also utilizes a cylindrical housing 91 having threaded end caps 111 and 112. A three-sectional plastic balloon 92-9394 is employed in this embodiment as the expansible container. The midsection 93 of this balloon is more expansible than the end-sections 92 and 94, and it expands when pressurized to force lever arm 95 upward until microswitch 96 is actuated to complete the circuit between terminals 59 and 61 which are mounted on and through cylindrical housing 91. Lever arm 95 is pivoted at fulcrum 103 of support 104 and is counterbalanced at end 97 to reduce the possibility of accidental closing of microswitch 96 due to vibration or shock and also to ensure that pressure applied to microswitch 96 is uniform regardless of the position of the device. In its normal condition, end 98 of lever arm 95 rests upon support 106. Expansible container 92-93-94 is fixed to a support member 105 by any suitable means at points 101 and 102 attached to the end-sections 92 and 94, respectively. Expansible container 92-93-94 is equipped with a valve stem 99, extending through an opening in support 106, so that it may be inflated to any desired pressure. The structure for supporting expansible container 92-93-94 and lever arm 95, which comprises supports 104, 105 and 106, is fixed to housing 91 by support members 107 and 108. Microswitch 96 is positioned adjacent the counterbalance end of lever arm 95 by support member 109. A bimetallic strip is utilized for lever arm 95 to compensate for temperature variations. However, accurate timing may also be obtained with an uncompensated device by merely adjusting the chamber pressure to the proper level for the expected operating temperature. Small variations in temperature have little effect on timing accuracy because the increased pressure in the chamber that would accompany an increase in temperature would be compensated for by a corresponding increase in pressure within the expansible member due to the same increase in temperature. The time required for the pressure within the chamber to decrease to some predetermined level would increase when the pressure is increased due to the increase in temperature but this would be compensated for by an increased pressure within the expansible member which would cause the microswitch to be actuated under conditions of higher chamber pressure than at a lower temperature.

A fourth embodiment of the invention is illustrated in FIG. 4 which is basically similar to the embodiment of FIG. 3 with the exception of the configuration for the expansible container. In FIG. 4 an oblong-type container 35 is employed rather than the three-sectioned container 92-93-94 of FIG. 3. The expansible container of this embodiment is much simpler to manufacture than the three-section container of FIG. 3 and is used where simplicity is a major consideration. A rubber tube inflated and sealed at both ends is sufficient for the expansible container 35 in the embodiment of FIG. 4. In practice, the rubber tube is inflated until it just touches counterbalanced lever arm 95 so that a decrease in internal pressure caused by the air discharging through a metering valve (not shown) attached to pipe 113 causes the balloon to expand an additional amount to force lever arm 95 in the upward direction so that the counterbalance end 97 triggers microswitch 96. The lever arm of this embodiment is similar to that of the embodiment of FIG. 3 and is constructed of bimetallic material for temperature compensation. Both of the embodiments of FIGS. 3 and 4 are vibration and shock resistant by virtue of the counterbalanced lever arm. The expansible member in both embodiments of FIGS. 3 and 4 is equipped with a valve stem 99 extending through an opening of support 106 so that it may be inflated to any desired pressure.

In the embodiments of FIGS. 3 and 4, a valve (not shown) for allowing air to be forced into the chamber thereby pressuring the chamber is attached to port 113. The same valve may be used to allow air discharge from the chamber at the preselected time. Separate valves may be provided at port 113 for each function in accordance with the embodiments illustrated in FIGS. 1 and 2.

In the case where the expansible member is inflated at room temperature and the device is to be operated at very low temperature, it is necessary to insure that the pressure within the expansible member is sufficient to close the switch at the minimum temperature of its intended environment. The time delay for switch closing is controlled by selecting the proper orifice opening of the valve through which the air discharges and by pressurizing the chamber to a given level for the operating temperature anticipated. In practice, pressure temperature-time monographs would be available for each discharge orifice.

In the embodiments of FIGS. 1 and 2 utilization of the spherical expansible member pressurized and then sealed eliminates valve stem 99 shown in FIGS. 3 and 4 thereby reducing size and weight. This also eliminates the possibility of a leaky container valve. In those embodiments (of FIG. I and 2) either a single switch or a pair of serially connected switches may be employed within the screen enclosure. The dual switches as illustrated provide a higher degree of protection against accidental closing clue to vibration or shock. In certain cases it may also be desired to employ microswitches rather than the contact-type switches for the embodiment of FIG. 1.

It is to be understood that any fluid may be used in the pressurized chamber of the various embodiments of this invention. Though the invention has been described with reference to air in the chamber, any other suitable fluid may be used. How ever, air or some other gas will probably be used in most environments. It should also be noted that a normally closed switch may be used in the embodiments of FIGS. 2, 3 and 4. A normally closed switch may also be employed in the embodiment of FIG. 1 if the operation of the device is inverted so that the expansible member 35 is initially in the fully expanded position so that the switch contacts are normally engaged. The circuit is then broken when the chamber is pressurized to contract the expansible member. In other words the operation would be the inverse of that described. This inverse operation may also be applied to the embodiments of FIGS. 2, 3 and 4, wherein the microswitches shown therein would be in the normally actuated position so that the circuit is closed and wherein the circuit is open when the chamber is pressurized to force the expansible member to contract.

In summary, the present invention provides a time-delay device wherein a switch within a fluidtight housing is actuated in response to an expansible member. Air or any other suitable fluid may be employed to pressurize the chamber. At a predetermined future time, the pressurized air is allowed to discharge from the housing at a predetermined rate proportional to the amount of time-delay desired so that the expansible member expands at a rate proportional to the rate of discharge of the pressurized air. The device provides a reliable time-delay switch for opening or closing an electric circuit at a preselected future time. Obviously many other modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A time-delay device comprising:

a hollow capsule enclosing a chamber,

a first valve means for allowing fluid to be forced into said chamber,

a second valve means for allowing fluid within said chamber to discharge from said chamber when said second valve means is open,

an expansible member within said capsule,

a first fixed contact attached to said capsule and electrically insulated from said capsule,

electrically conductive spring means attached to said capsule and insulated therefrom,

a second contact attached to said spring means,

first electrical coupling means mounted on said capsule and insulated therefrom,

second electrical coupling means mounted on and insulated from said capsule,

means for electrically connecting said first fixed contact to said first electrical coupling, and

means for electrically connecting said electrically conductive spring means to said second electrical coupling means,

whereby said expansible member expands at the rate of said fluid flow from said chamber through said second valve means and said expansible member moves said second contact into electrical engagement with said first contact when said expansible member expands to a predetermined volume.

2. A time-delay device comprising:

a fluidtight hollow capsule enclosing a chamber,

a spherical screen in said chamber,

support means attached to said hollow capsule for fixedly positioning said spherical screen within said chamber,

a first contact positioned on said spherical screen and insulated therefrom,

spring means mounted on said spherical screen,

a second contact mounted on said spring means adjacent said first contact, said first and second contacts forming a normally open switch,

first and second electrical terminals mounted on and insulated from said hollow capsule and extending therethrough in sealing engagement therewith,

first electrical means interconnecting said first contact means with said first electrical terminal,

second electrical means interconnecting said spring means with said second electrical terminal,

an expansible member freely positioned within said spherical screen,

a first valve mounted on said hollow capsule and extending through said hollow capsule into said chamber for allowing fluid to be forced into said chamber,

a second valve on said hollow capsule for allowing fluid to be discharged from said chamber when said second valve is open,

whereby said expansible member expands at the rate of said fluid flow from said chamber through said second valve and said expansible member moves said second contact into electrical engagement with said first contact when said expansible member expands to a predetermined volume.

3. A timer comprising:

a fluid tight hollow capsule enclosing a chamber,

a spherical screen supported within said capsule,

a normally open switch mounted with said spherical screen and supported by said spherical screen,

an expansible member freely positioned within said spherical screen,

first means coupled to said hollow capsule for allowing fluid to be forced into said chamber,

fluid flow from said chamber through said second means, said expansible member closing sai switch when said expansible member is expanded to a predetermined volume. 4. A timer in accordance with claim 7 wherein said switch 10 comprises a microswitch mounted within and attached to said spherical screen.

5. A timer in accordance with claim 7 wherein said switch comprises:

a first contact mounted within and attached to said spherical screen,

spring means mounted within and attached to said spherical screen,

a second contact mounted on said screen means adjacent said first contact to form a normally open switch with said first contact.

6. A timer comprising:

a fluid tight capsule enclosing a chamber,

an expansible member having a first, second and third section, said section section being more expansible than said first and third sections,

valve means extending from said expansible member for inflating said expansible member,

a normally open switch within said capsule,

means for electrically connecting said switch externally to said capsule,

means responsive to the expansion of said second section of said expansible member for actuating said microswitch, and

means coupled to said capsule for pressurizing said capsule and for allowing fluid communication between said chamber and its environment.

7. The timer of claim 6 wherein said housing comprises:

a tubular member, and

a first and second end-cap at each end of said tubular member in fluid tight coupling therewith.

8. The timer of claim 6 wherein said switch is a microswitch.

9. The timer of claim 6 wherein said means responsive to the expansion of said expansible member for actuating said microswitch is a pivoted lever arm.

10. A timer as set forth in claim 9 wherein said lever arm is of bimetallic structure.

11. A time-delay device comprising:

a hollow cylindrical housing,

a switch mounted within said housing,

an expansible member within said housing,

means within said housing for inflating said expansible member,

means responsive to the expansion of said expansible member for actuating said switch,

means within said housing electrically coupling said switch externally to said housing,

means for pressurizing said housing and for allowing fluid communication between the interior of said housing and its exterior, and

means at both ends of said cylindrical housing for maintaining said housing normally fluid tight.

12. A TIME-delay device as recited in claim 11 wherein said means responsive to said expanding expansible member is a pivoted lever arm.

13. The time-delay device of claim 12 wherein said switch is a normally open microswitch.

14. The device of claim 13 wherein said lever arm is of bimetallic structure. 

1. A time-delay device comprising: a hollow capsule enclosing a chamber, a first valve means for allowing fluid to be forced into said chamber, a second valve means for allowing fluid within said chamber to discharge from said chamber when said second valve means is open, an expansible member within said capsule, a first fixed contact attached to said capsule and electrically insulated from said capsule, electrically conductive spring means attached to said capsule and insulated therefrom, a second contact attached to said spring means, first electrical coupling means mounted on said capsule and insulated therefrom, second electrical coupling means mounted on and insulated from said capsule, means for electrically connecting said first fixed contact to said first electrical coupling, and means for electrically connecting said electrically conductive spring means to said second electrical coupling means, whereby said expansible member expands at the rate of said fluid flow from said chamber through said second valve means and said expansible member moves said second contact into electrical engagement with said first contact when said expansible member expands to a predetermined volume.
 2. A time-delay device comprising: a fluidtight hollow capsule enclosing a chamber, a spherical screen in said chamber, support means attached to said hollow capsule for fixedly positioning said spherical screen within said chamber, a first contact positioned on said spherical screen and insulated therefrom, spring means mounted on said spherical screen, a second contact mounted on said spring means adjacent said first contact, said first and second contacts forming a normally open switch, first and second electrical terminals mounted on and insulated from said hollow capsule and extending therethrough in sealing engagement therewith, first electrical means interconnecting said first contact means with said first electrical terminal, second electrical means interconnecting said spring means with said second electrical terminal, an expansible member freely positioned within said spherIcal screen, a first valve mounted on said hollow capsule and extending through said hollow capsule into said chamber for allowing fluid to be forced into said chamber, a second valve on said hollow capsule for allowing fluid to be discharged from said chamber when said second valve is open, whereby said expansible member expands at the rate of said fluid flow from said chamber through said second valve and said expansible member moves said second contact into electrical engagement with said first contact when said expansible member expands to a predetermined volume.
 3. A timer comprising: a fluid tight hollow capsule enclosing a chamber, a spherical screen supported within said capsule, a normally open switch mounted with said spherical screen and supported by said spherical screen, an expansible member freely positioned within said spherical screen, first means coupled to said hollow capsule for allowing fluid to be forced into said chamber, second means coupled to said hollow capsule for allowing fluid to be discharged from said chamber when said second means opened, whereby said expansible member expands when said second means is opened at a rate proportional to the rate of said fluid flow from said chamber through said second means, said expansible member closing said switch when said expansible member is expanded to a predetermined volume.
 4. A timer in accordance with claim 7 wherein said switch comprises a microswitch mounted within and attached to said spherical screen.
 5. A timer in accordance with claim 7 wherein said switch comprises: a first contact mounted within and attached to said spherical screen, spring means mounted within and attached to said spherical screen, a second contact mounted on said screen means adjacent said first contact to form a normally open switch with said first contact.
 6. A timer comprising: a fluid tight capsule enclosing a chamber, an expansible member having a first, second and third section, said section section being more expansible than said first and third sections, valve means extending from said expansible member for inflating said expansible member, a normally open switch within said capsule, means for electrically connecting said switch externally to said capsule, means responsive to the expansion of said second section of said expansible member for actuating said microswitch, and means coupled to said capsule for pressurizing said capsule and for allowing fluid communication between said chamber and its environment.
 7. The timer of claim 6 wherein said housing comprises: a tubular member, and a first and second end-cap at each end of said tubular member in fluid tight coupling therewith.
 8. The timer of claim 6 wherein said switch is a microswitch.
 9. The timer of claim 6 wherein said means responsive to the expansion of said expansible member for actuating said microswitch is a pivoted lever arm.
 10. A timer as set forth in claim 9 wherein said lever arm is of bimetallic structure.
 11. A time-delay device comprising: a hollow cylindrical housing, a switch mounted within said housing, an expansible member within said housing, means within said housing for inflating said expansible member, means responsive to the expansion of said expansible member for actuating said switch, means within said housing electrically coupling said switch externally to said housing, means for pressurizing said housing and for allowing fluid communication between the interior of said housing and its exterior, and means at both ends of said cylindrical housing for maintaining said housing normally fluid tight.
 12. A TIME-delay device as recited in claim 11 wherein said means responsive to said expanding expansible member is a pivoted lever arm.
 13. The time-delay device of claim 12 wherein said switch is a normally open microswitch.
 14. The device of claim 13 whereiN said lever arm is of bimetallic structure. 